Optical fiber connector assembly

ABSTRACT

An optical fiber connector includes a connector housing having first and second generally parallel, spaced apart first and second faces and at least one generally cylindrical receptacle for removably receiving an optical fiber terminus therein. An optical fiber terminus is located within the receptacle and includes an elongated body with a passage along a central axis for receiving a portion of an optical fiber cable therethrough. The body further includes an indexing section, and a ferrule secured to the body and having an end portion of said optical fiber cable therein. A collar is positioned on the elongated body and has an engagement section for engaging the indexing section. The collar is movable along the axis between first and second operative positions. In the first operative position relative rotational movement between the collar and the body is prevented and in the second operative position the collar may rotate relative to the body. A biasing member is provided to bias the collar towards the first operative position.

REFERENCE TO RELATED APPLICATION

This application claims priority form prior U.S. Provisional patentapplication No. 60/636,879, filed Dec. 20, 2004.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for inter-connectingoptical devices and, more particularly, to a connector for terminatingan optical fiber.

Optical fiber connectors are an essential part of substantially anyoptical fiber based communication system. For instance, such connectorsmay be used to join segments of fiber into longer lengths, to connectfiber to active devices such as transceivers, detectors and repeaters,or to connect fiber to passive devices such as switches and attenuators.The central function of an optical fiber connector is to maintain orposition two optical fiber ends such that the core of one fiber isaxially aligned with the core of the other fiber. Consequently, thelight from one fiber is coupled to the other fiber or transferredbetween the fibers as efficiently as possible. This is a particularlychallenging task because the light-carrying region or core of an opticalfiber is quite small. In single mode optical fibers, the core diameteris about 9 microns. In multi-mode fibers, the core can be as large as62.5 to 100 microns, and hence alignment is less critical. However,precision alignment is still a necessary feature to effectivelyinterconnect the optical fibers.

Another function of the optical fiber connector is to provide mechanicalstability to and protection for the optical junction in its workingenvironment. Achieving low insertion loss in coupling two fibers isgenerally a function of the alignment of the fiber ends, the width ofthe gap between the ends, and the optical surface condition of either orboth ends. Stability and junction protection is generally a function ofconnector design (e.g., minimization of the different thermal expansionand mechanical movement effects). Precision alignment of the opticalfiber is typically accomplished within the design of the opticalterminus assembly. The typical optical terminus assembly utilizes amethod of retention of the terminus within the connector(s) integratedwithin it and a method of holding and aligning the optical fiber. Toalign the optical fiber, a terminus typically includes a small cylinderof metal or ceramic at one end commonly referred to as a “ferrule.” Theferrule has a high precision hole passing along it centerline and glassor plastic optical fiber can be installed into the hole within theferrule using mechanical, adhesive or other retention methods. Theprimary operational sections of an optical terminus are the supportstructure around the ferrule and the mechanism (typically a spring) usedto create a force to push the ferrule into an opposing ferrule of amating optical connector.

In a connection between a pair of optical fibers, a pair of ferrules isbutted together in an end to end manner and light travels from one tothe other along their common central axis. In this conventional opticalconnection, it is highly desirable for the cores of the glass fibers tobe precisely aligned in order to minimize the loss of light (such lossbeing referred to as insertion loss) caused by the connection. As onemight expect, it is presently impossible to make a perfect connection.Manufacturing tolerances may approach “zero” but practicalconsiderations such as cost, and the fact that slight misalignment istolerable, suggest that perfection is unnecessary although stabilityacross the operating environment of the fiber joint is critical.

Historically, due to manufacturing costs and design features, opticaltermini have tended to be manufactured as an assembly of loosecomponents. In high performance connectors intended for single modeapplication, there exists a specific need to tune out the eccentricityof assemblies and such tuning has been achieved by the interactionbetween the terminus or ferrule support structure and the connectorhousing. This is an undesirable effect as the housing becomes anintegral element in tuning and if the terminus is removed from thehousing (such as for cleaning or replacement), the tuning is in effectlost.

Optical terminus assembly tuning is used to reduce the random positionof the optical fiber within an optical connector. The randomness of thispositioning may be in the order of fractions of microns to severalmicrons. However, when consideration is taken of single mode opticalfiber with an optical waveguide of only 8-9 microns in diameter, it canbe seen how optical insertion loss can be dramatically impacted ifcontrol of the placement of the optical core is not maintained. Fibereccentricity compensation is currently most commonly found on singlechannel “LC” style connectors. Compensation is attained using a facetedstructure (such as a square or hexagon) to register on the front end ofthe ferrule support structure. The support structure engages anappropriate complementary pattern within the LC connector body andretains positioning by engaging the LC body. Thus tuning or fibereccentricity compensation is only retained as the ferrule and itssupport is retained within the connector body. Once removed it is notpossible to determine the exact positional relationship between thefiber holding structure and the connector body.

Recognizing the engineering challenge posed by the alignment of two verysmall optical fiber cores, it is desirable to provide termini that aresmaller, less expensive, and yet more convenient for customers tomanipulate. One of the key features associated with the design oftermini is the system for retaining the termini in a connector. Theretention feature affects the ability of the terminus to be engaged intoa connector system and retained within the connector system duringmating of the two connector halves. The retention system must enableusers of the optical terminus system and its associated connector systemthe ability to remove the optical termini individually for service,repair, inspection or other reasons. Existing optical termini systemsare typically utilized in military connector systems and some designsincorporate anti-rotation features but none include an operativeretention system and tuning capability as an integral part of theterminus.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a terminus retentionsystem that removes complexity from the connector system and enablesusers to quickly service connectors, yet retain the tuning of aterminus. As such, a connector is disclosed for terminating an opticalfiber including a fiber holding structure for maintaining eccentricitycompensation and having an end face in which an associated fiber isterminated within the holding structure and including an axialpassageway which terminates in the end face and which is adapted toreceive an end portion of the associated optical fiber. A connectorhousing has internal surfaces that define a cavity to accept thefiber-holding structure and includes first and second openings extendinginto the cavity and being positioned at opposite ends of the housing.The first opening is configured to receive an optical fiber and thesecond opening is configured to enable the end face of the holdingstructure to protrude through the opening. A latch is provided integralto the fiber holding structure to secure the fiber holding structurewithin an associated cavity. To preclude unintended decouplingtherebetween, the latch includes a protrusion positioned on one or moresurfaces of a sliding collar integral to the fiber holding structure.The latch is configured to engage the cavity structure by having theprotrusion sweep an arc beneath an upper surface of the cavity. When thelatch protrusion is swept through the arc, it is held beneath the rearface of the cavity by spring pressure created by compression of aprimarily helical spring coaxially located along the fiber holdingstructure longitudinal axis.

In the preferred embodiment, the spring member interacts between twosurfaces within the fiber-holding structure. The fiber holding structurealso provides a keying structure to engage the housing and likewise urgean end face or ferrule through the second opening in the housing.

The terminus is a cylindrical fiber-holding structure with a ferrulethat includes the end face in which the associated fiber is terminatedand an axial passageway which terminates in the end face. Thispassageway is adapted to receive an uncoated end portion of theassociated fiber. A base member holds an end portion of the ferrulewithin the terminus assembly and includes an axial passageway which iscollinear with the axial passageway of the ferrule. A shoulder may alsobe provided to engage a spring of the terminus assembly. A rear portionof the base member provides a multi-positional eccentricity indexfeature, such as a hexagonal section. A sliding collar which has ashoulder to engage a spring, an axial pass way in which the base memberassembly is positioned and an external index “key” formed by one or moreprotrusions. A spring member is provided to push the sliding collartowards the rear of the base member. In one embodiment, the cylindricalferrule has a diameter of about 1.25 millimeters.

The cylindrical plug of the present invention includes a tube whoseouter cylinder surface has a circular cross section and whose axialpassageway is substantially concentric with the outer cylinder surfaceand wherein the tube is made from ceramic or metallic materials. Thefiber-holding structure is adapted to be held within the housing in asingular stable angular position such that the angular position of thefiber-holding structure with respect to the housing is constant. Inaddition, the fiber-holding structure sliding collar index key allowsthe entire fiber-holding structure to be removed from the connectorhousing yet maintain its singular stable angular position when returnedto the connector housing. The connector housing includes first andsecond interconnecting housing members which each include an internalcavity for receiving the fiber-carrying structure. The secondinterconnecting member is generally cylindrical in shape so as to matewith the first interconnecting member. The first and secondinterconnecting members combine to form a structure that substantiallyencloses the fiber-holding structure. The first and secondinterconnecting members are made from a metallic, plastic or ceramicmaterial and are secured together using a positive locking device suchas a threaded collar, a coupling screw or external physical clamp.

An optical cable and a connector are also disclosed in which the opticalcable includes a glass fiber enclosed within a plastic buffer materialand the connector includes a fiber-holding structure with an axialpassageway which receives the optical fiber and which terminates in aplanar end face that is perpendicular to the passageway. A housing hasinternal surfaces that define a cavity and surround the fiber-holdingstructure as well as a first opening at the back end of the housingwhich receives the optical cable and a second opening at the front endof the housing through which the end face of the fiber-holding structureprotrudes. The openings extend into the cavity and are positioned atopposite ends of the housing. The housing captures the fiber holdingstructure in a manner such that eccentricity is confined to a unique,known position. A manually operated latch for securing the fiber holdingstructure to the associated receptacle is also provided to precludeunintended decoupling therebetween. The latch is positioned on a one ormore side surfaces of the sliding collar section integrated within thefiber holding structure. The latch includes a spring element containedwithin the fiber holding structure. The fiber-holding structure includesan annular spring that interacts with two flanges or shoulders withinthe fiber-holding structure. One of the shoulders is free to moverelative to the other along the primary axis of the fiber-holdingstructure and engages the housing thus urging the end face of thefiber-holding structure through the second opening in the housing.

A connector for terminating an optical fiber includes a fiber-holdingstructure that terminates in an end face and is adapted to receive anend portion of the optical fiber. A housing includes a plurality ofinternal surfaces that define a cavity and surround the fiber-holdingstructure, a first opening for receiving an optical fiber holdingstructure/optical fiber and a second opening for enabling the end faceof the fiber-holding structure to protrude therethrough. The openingsextend into the cavity and are positioned at opposite ends of an axialpassageway through the housing. The fiber-holding structure includes acompression spring which presses two shoulders or flanges on the fiberholding structure. The flanges are free to move axially relative to oneanother to urge the end face of the fiber-holding structure through thesecond opening in the housing.

An optical fiber connector is disclosed for effecting optical end-to-endcoupling between two optical fibers, each of which terminates in aferrule having a precision cylindrical outside surface. One end of eachferrule is held within an opening in a base member. The base member isgenerally cylindrical and has a flange which is disposed around thecircumference of the base member and interacts with one end of anannular spring which is also disposed around the base member. Theferrule, base member and spring are joined to a secondary member thatincludes a hexagonal or other even sided geometric shaped indexingfeature. A sliding member including a latch protrusion feature thatengages the secondary member to permit indexing of the hexagonal orother even sided geometric shaped indexing feature and further engages aconnector body housing. This engagement is accomplished with one or moreunique indexing keys that extend approximately perpendicular to thelongitudinal axis of the siding member and engage an appropriate slot inthe connector body housing.

An optical fiber terminus body has a helical spring trapped betweenfront shoulder on a main inner body and a rear shoulder created by athin flange on a sliding collar. The sliding collar is likewise trappedbetween the rear of the spring and a rear shoulder on the main innerbody. Typically, the inner body is formed using two components that arepressed, bonded, welded or otherwise assembled. The collar has analignment ring on it to retain precise alignment of the terminus withina stepped cylindrical bore. The collar also has a protrusion thatenables keying and positive positioning of the terminus assembly withina stepped cylindrical bore when the bore has an appropriate slot formedin it or a slot that is created with a secondary piece. The slot isconfigured with a cut that extends along an arc around the axis of thebore so that the protrusion can act as a retainer mechanism for theterminus assembly in the cylindrical bore. This is accomplished byinserting the terminus into the bore until the front edge of the sectionhaving the front spring retention shoulder engages a step in the bore.This presents further penetration of the terminus assembly through thestepped bore. At that time, the sliding collar begins to move forwardalong the main inner body. The protrusion on the collar moves throughthe slot along the side of the bore and the spring is compressed. As theprotrusion on the collar reaches the end of the slot in the bore, it canbe rotated in an undercut arc in the bore. When rotated to the end ofthe arc, the protrusion cannot pass back upward along the axis of thebore. Hence, there remains compression of the spring and the entireassembly is captured within the bore by the spring pressure between thefront shoulder on the main inner body and the sliding collar that hasengaged the cylindrical bore. To facilitate tuning of the terminus, ahexagonal or other faceted shaped section integral to the main terminusbody is provided at the rear of the main terminus body and engages thesliding collar. The hexagonal or other faceted shaped section isincluded to allow tuning or minimization of eccentricity of the internalbore relative to a mating terminus of the same type. Tuning isaccomplished by determining a desired position for the offset in thebore centerline in the main inner body relative to the sliding collar.If a hexagonal tuning section is used, one of six positions isavailable. The sliding collar engages one of the available tuningsections on the main inner bodies. These and other objects, features andadvantages of the present invention will be clearly understood through aconsideration of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the present invention will be understoodfrom the following description according to one preferred embodiment ofthe present invention which is shown in accompanying drawings in which:

FIG. 1 is a perspective view of one embodiment of an optical fiberterminus in accordance with the principles of the present invention;

FIG. 2 is an exploded perspective view of the optical fiber terminus ofFIG. 1;

FIG. 3 is a side elevational view of the optical fiber terminus of FIG.1;

FIG. 4 is a perspective view of one embodiment of an optical fiberconnector in accordance with the principles of the present inventionincluding a plurality of optical fiber termini of FIG. 1 mountedtherein;

FIG. 5 is a partially exploded perspective view of the optical fiberconnector of FIG. 4 from a different orientation with a central portionof the connector housing removed from an outer shell of the connector;

FIG. 6 is an exploded perspective view of the central portion of theconnector housing together with a plurality of optical fiber termini;

FIGS. 7A-7D are perspective views of the optical fiber terminus showinga portion of the sequence of tuning the optical fiber terminus byaxially moving and rotating the sliding collar relative to the innermain body; and

FIGS. 8A-8D are perspective views, partially in section, of the opticalfiber terminus and central portion of the connector housing showing thesequence of insertion of the optical fiber terminus into the housing andlocking of the terminus therein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with one embodiment of the present invention and referringfirst to FIGS. 1 and 4, an optical fiber support assembly or terminus 10and an optical fiber connector 60 that includes a plurality of termini,as well as a method of assembly, are disclosed. The terminus includesthree main components, inner main body or member 12, a sliding collar orouter member 14 with protrusion boss or tab 16 extending radiallytherefrom and substantially helical spring or biasing member 18. Theinner main body is typically an assembly of three components (FIG. 2) aferrule 20 (typically made of ceramic or metal), a forward section orbody 22 that is joined to the ferrule with an adhesive or by a press-fitand a rear section or body 24 that is assembled with forward section 22and captures the sliding collar and helical spring 18 therebetween. Asdescribed in more detail below, sliding collar 16 is indexable throughthe interaction between registration structure integral to the collarand indexing structure integral to the rear of inner main body. Thesliding collar is further indexed relative to the connector assembly bythe interaction of features included in the connector body and theprotrusion on the sliding collar.

As described above, the terminus 10 has a ferrule 20 attached to theinner main body to position an optical fiber along the longitudinalcenterline or axis “A” of the terminus assembly. The terminus has anopening or bore 26 therein for receiving an end of an optical fiber. Theinner main body 12 has a shaft portion 28 (FIGS. 1 and 3) formed by thecombination of forward section 22 and rear section 24 about which thespring 18 can be positioned and aligned. A forward shoulder 30 on mainbody 12 forms a front abutment that abuts a front end 32 of the spring,and a shaft recess forming a shoulder. Sliding collar 14 is alsoinstalled onto the shaft portion 28 of the main inner body 12 adjacentspring 18.

Sliding collar forms the rear abutment 34 that abuts the rear end 36 ofthe spring. An engagement section 38 is formed at the rear of collar 14with opposing arms 42 having inwardly facing flat surfaces 44. The flatsurfaces 44 of the arms engage a multi-faceted (typically hexagon)indexing section 40 on the rearward end of the inner main body. Opposingarms 42 engage opposite sides of the hexagonal indexing section 40 toprevent rotation of the collar 14 relative to the inner main body 12 andfurther enable selection of multiple orientations of the inner main bodyrelative to the collar 14 and the protrusion boss 16 projectingtherefrom. The main terminus body 12 has a rear shoulder 46 thatprevents the collar 16 and spring 18 from sliding off the shaft 28 andprovides a pre-load compression of the spring when assembled. The mainterminus body 12 is typically a two piece component that is either pressfit together, bonded together, welded together or affixed together intoa single piece using another method of securement. The assembly offerrule 20, main terminus body 12, spring 18 and sliding collar 16 iscommonly referred to as a terminus assembly.

Referring to FIGS. 4-6, the terminus assembly 10 must be retained withina connector housing or body 62 in order to form a single or multipleoptical pathways interconnect system. An interconnect system istypically formed with a plug connector (not shown) and a matingreceptacle connector 60. During mating, opposing optical termini arebrought into direct end face contact with one another and the opticalfiber (shown in phantom lines in FIG. 1) positioned within each terminusare optically coupled together. When mating of the optical termini isproperly implemented, a very low optical loss interconnection is formed.When utilizing termini of the present invention, arrays of very dense,very high performance optical interconnect solutions can be formed.

The terminus assembly 10 is retained within connector housing 62 throughthe interaction between the protrusion boss 16 on sliding collar 14 andstructure of the connector housing. Retention is achieved when theterminus assembly 12 is installed into a principally cylindrical bore orterminus cavity 64 within a connector housing or body 62. In thepreferred embodiment, the connector housing is formed from twocomponents, a front housing member 66 and a rear housing member 68. Thefront and rear housing members are made of metal, plastic or ceramic andare held together by a positive locking device such as a coupling screw69 although other devices such as a threaded collar or an externalphysical clamp could be used.

The terminus cavity has two or more primary diameters. A smaller,forward diameter 70 generally approximates the diameter of the ferrule20 and is smaller than the diameter of the leading section 52 of forwardsection 22 into which the ferrule is pressed. The largest diameter 72 inthe terminus cavity is adjacent the rear of the connector and thisdiameter is slightly larger than the diameter of the main body 48 of thesliding collar. In the embodiment shown, the sliding collar has a fullperiphery precision shoulder 50 that interacts with the rear borediameter 72 to provide very precise alignment of the sliding collar 14with respect to the rear bore diameter of the terminus cavity. This isdesirable to maintain axial alignment of the entire optical terminiassembly 10 relative to the axis of the terminus cavity. Other methodsof precision alignment may be feasible such as multiple raised sectionsor a precision machined main body for the sliding collar.

Referring to FIG. 6, the rear opening 74 of the bore in the terminuscavity 64 has a slot 76 extending from a rear face 78 of the housingalong an edge of the bore a relatively short distance into the terminuscavity. An arcuate retention slot or recess 80 extends along an arc fromthe slot 76 with the arc being formed about the central axis “B” of thecavity and principally perpendicular to the slot. This arcuate recessforms a turning section adjacent the slot that extends generally at aright angle to axis B. A small recess 82 is added at the end of the arcin a direction parallel to the central axis of the cavity for receivingthe protrusion boss 16 of sliding collar 14 to secure the terminusassembly 10 in the housing as described below.

During assembly, the terminus assembly is retained within the housing bypositioning the terminus assembly 10 at the rear of the terminus cavity64 with protrusion boss 16 and slot 76 aligned as shown in FIG. 8A andmoving terminus assembly 10 along the central axis B of the cavity 64 bygripping or engaging the sliding collar 14 with an appropriate tool (notshown). This forward movement continues until the front or forward edgeor shoulder 52 of the inner terminus body engages the forward wall 84 ofthe smaller diameter bore 70 in the terminus cavity. The ferrule 20 willbe extending through front face 86 of the terminus cavity bore andpositions the terminus assembly 10 to substantially a central locationalong the terminus cavity 64 so that the central axis B of the cavityand the central axis A of the terminus assembly coincide. When frontedge 52 of the terminus inner body 12 engages the front face in theterminus cavity, forward movement of inner body 12 is stopped. Bycontinuing to apply force to sliding collar 14, collar 14 continues tomove forward relative to terminus inner body 12 and, thus, alsocompressing spring 18 that is an integral part of terminus assembly 10.(FIG. 8B) The protrusion boss 16 on the terminus collar 14 is alignedwith the slot in the wall of the terminus cavity and passes along ituntil it reaches the end of the slot. Preferably, the opposing arms 42of collar 14 and hexagonal indexing section 40 are dimensioned so thatarms 42 still engage indexing section 40 when protrusion boss 16 reachesthe end of the terminus cavity slot. Through such structure, the tuningof terminus assembly 10 is not affected or changed during insertion ofthe assembly into the terminus cavity.

Referring to FIG. 8C, once protrusion boss 16 abuts the end of slot 76,the collar 14 and entire terminus assembly 10 are rotated together aboutthe axis B of the terminus cavity with protrusion boss 16 travelingthrough arcuate retention slot 80 until the protrusion boss 16 engagesthe end wall 88 of the arcuate retention slot. As force is released fromthe collar 14 such as by a technician installing the terminus assembly,spring 18 provides a force that pushes collar 14 axially rearward sothat protrusion boss 16 enters recess 82 at the end of the arcuateretention slot 80 to retain the protrusion boss therein (FIG. 8D). Thisspring force maintains the terminus assembly 10 both radially andaxially in the terminus cavity bore 64 and hence within the connectorassembly 60. In other words, the orientation of the terminus assembly isretained in a predetermined position since the position of collar 14 isdetermined by the location of the arcuate retention slot, and theterminus inner body 12 is fixed relative to collar 14 by the indexingfeatures, as described above. In industrial vernacular, the terminusretention system described above is known as a “quarter turn” fastener,although in the present embodiment, the quarter turn fastener ismodified in that only a single protrusion boss 16 is used. In addition,the single protrusion boss 16 is what enables tuning of the opticalconnector system.

The present invention incorporates an optical ferrule holding structure10, termed the optical terminus assembly and a support structure, termedthe connector. The connector has an optical terminus cavity for eachchannel in a single or multiple channel connector system. The cavity hasa “key” feature that identifies positional location for proper tuning byaligning the protrusion boss 16 feature on the sliding collar 14 ofopposing termini to be in-line. In this manner, by establishingeccentricity compensation relative to the protrusion boss, the relativeeccentricity of two mating ferrules will be minimized and the resultingoptical loss likewise minimized. Further, according to the presentinvention, by properly positioning the boss and retaining it within theconnector body, the entire assembly can retain its eccentricitycompensation even when the fiber support structure or terminus 10 isremoved from the connector body.

Since retaining eccentricity compensation is a key feature of thedisclosed invention, it is important to understand the eccentricityissues. Alignment variations between a pair of interconnected ferrules20 are principally attributable to the parameter known as “eccentricity”of the optical fiber core with respect to the ferrule. Eccentricity isdefined as the distance between the longitudinal centroidal axis of theferrule at an end face of the ferrule and the centroidal axis of theoptical fiber core held within the passageway of the ferrule. Generally,the passageway is not exactly concentric with the outer cylindricalsurface that is the reference surface. Also, the optical fiber may notbe exactly centered within the ferrule passageway and the fiber core maynot be exactly concentric with the outer surface of the fiber. Hence,the eccentricity is comprised of the eccentricity of the optical fiberwithin the ferrule passageway and the eccentricity of the passagewaywithin the ferrule.

If one could view the end portion of a “lit” optical fiber, what wouldbe seen is a circle with a dot of light somewhat displaced from theexact center of the circle. Eccentricity can be understood as atwo-dimensional vector having magnitude and direction components. The“magnitude component” of the eccentricity vector is the straight linedistance between the center of the circle and the dot of light, whilethe “direction component” of the eccentricity vector is the angle madeby that straight line with respect to the X-axis of a 2-dimensionalCartesian coordinate system whose origin is at the center of the circle.It is noted that ferrules used in conventional optical connectors (i.e.,ST, SC and FC) have a 2.5 mm diameter while the ferrule disclosed in apreferred embodiment of the present invention has a diameter of 1.25 mmas utilized by the LC connection system. With the use of the smallerferrule, the magnitude component of the eccentricity vector isproportionally reduced and thus precision is improved.

Rotating one of two interconnected ferrules typically changes therelative position of the fibers held within their passageways because ofthe eccentricity of the optical fiber cores with respect to theferrules. Because it is very difficult to control the eccentricity ofthe optical fiber core in the ferrule in which it is terminated, it isdifficult to achieve desired losses of 0.1 dB or less in single modefibers without maintaining close tolerances so that the opposed coresare aligned to within about 0.7 microns. This scale of precisionincreases the manufacturing cost. If the total eccentricities of the twooptical fiber ends to be joined are identical, or at least very nearlyso, then a low-loss connection can be achieved by merely rotating,within the collar 14, one ferrule 20 with respect to the other, untilmaximum coupling is observed (minimum insertion loss).

Referring to FIGS. 7A-7D, the present invention enables fibereccentricity to be compensated through the use of an indexing slot 44between arms 42 in the terminus assembly 10. The terminus assembly 10 isdesigned such that it can be configured with one of six (hex) rotationalpositions relative to a master indexing key (protrusion boss 16 on thesliding collar 14). More or fewer registration features may be used. Thekey is an integral part of the sliding collar and although the preferredembodiment uses only one key, one or more keys may be used so long asunique orientation identification is retained.

Such a design enables the terminus assembly 10 to be installed in aconnector body in one of six rotational positions (0 degrees, 60degrees, 120 degrees, 180 degrees, 240 degrees, 300 degrees). Theparticular position selected is determined during fabrication of theconnector by measuring fiber eccentricity, linearly moving the innermain body 12 relative to collar 14 along axis A from a position (FIG.7A) in which relative rotation between inner main body 12 and collar 14is prevented by engagement between indexing slot 44 and indexing section40 a sufficient distance (as shown n FIG. 7B) to permit relativerotation between inner main body 12 and collar 14. The inner main body12 is then rotated relative to collar 14 (FIG. 7C) by an amount based onoptical power loss minimization measurement such that the arms 42 of theindexing slot 44 are aligned with indexing section 40. Once in thedesired rotational position, force is removed from collar 14 to permitspring 18 to bias collar away from ferrule 20 such that indexing slotengages indexing section 40 to prevent relative movement between theinner main body 12 and sliding collar 14.

The final requirement for a high optical performance connector is toalign the terminus assembly to a specific location when installed intothe connector body. As has been described above, this is accomplished byusing a slot in the terminus cavity. When mated connectors are broughttogether, their structures both provide for the retention of orientationrelative to the opposing optical terminus assemblies.

Although particular embodiments of the invention have been described andillustrated herein, it is recognized that modifications and variationsmay readily occur to those skilled in the art, and consequently, it isintended that the claims be interpreted to cover such modifications andequivalents. The novel features of the invention are set forth withparticularity in the appended claims. The invention will be bestunderstood from the following description when read in conjunction withthe accompanying drawings.

1. An optical fiber connector comprising: a connector housing havingfirst and second generally parallel, spaced apart first and second facesand at least one generally cylindrical receptacle for removablyreceiving an optical fiber terminus therein; and an optical fiberterminus within said receptacle, said terminus including an elongatedbody having a passage along a central axis with a portion of saidoptical fiber cable extending therethrough, said body further includingan indexing section, and a ferrule secured to said first section of saidbody and having an end portion of said optical fiber cable therein, acollar positioned on said elongated body and having an engagementsection for engaging said indexing section, the collar being movablealong said axis between first and second operative positions, said firstoperative position being wherein relative rotational movement betweensaid collar and said body is prevented and a second operative positionin which said collar may rotate relative to said body, and a biasingmember to bias said collar towards said first position.
 2. The opticalfiber connector of claim 1 further including a terminus locking memberand an arcuate recess through which said terminus locking member mayrotate from a first insertion position to a second locked position tolock said terminus within said receptacle.
 3. The optical fiberconnector of claim 2 wherein said terminus locking member is a bossextending from said terminus and said receptacle includes said arcuaterecess therein.
 4. The optical fiber connector of claim 3 including afirst opening in said first face and a second opening in said secondface, said ferrule extending through said first opening, said secondopening being round with a slot extending therefrom, and said lockingtab, said arcuate recess and said slot are dimensioned to permit saidtab to pass through said slot and travel into said arcuate recess. 5.The optical fiber connector of claim 4 wherein said slot extends in adirection parallel to said central axis and along an edge of said roundsecond opening.
 6. The optical fiber connector of claim 4 wherein saidarcuate recess includes a step for receiving said locking tab thereinwhen said terminus is locked in said cavity.
 7. The optical fiberconnector of claim 1 wherein said receptacle has a forward wall adjacentsaid first face and wherein said elongated body has a forward shoulderengaging said forward wall within said receptacle, said biasing memberexerting a spring force to bias said forward shoulder against saidforward wall.
 8. The optical fiber connector of claim 6 wherein saidreceptacle has a forward wall adjacent said first face and wherein saidelongated body has a forward shoulder engaging said forward wall withinsaid receptacle, said biasing member exerting a spring force to biassaid forward shoulder against said forward wall and bias said lockingtab within said step in said arcuate recess.
 9. An optical fiberconnector kit comprising: a connector housing having front and reargenerally parallel, spaced apart faces and at least one generallycylindrical receptacle extending therebetween for removably receiving anoptical fiber terminus therein, said receptacle having a terminuslocking surface adjacent said rear face, each of the faces having anopening therein; an optical fiber terminus configured to be positionedwithin said receptacle, said terminus including an elongated body havinga passage along a central axis for receiving a portion of said opticalfiber cable therethrough, said body including an indexing section, acollar having an engagement section for engaging the indexing sectionand a said terminus locking member for securing said terminus withinsaid receptacle, the collar being positioned on the elongated body andbeing movable along said axis between first and second operativepositions, said first operative position being wherein said engagementsection engages said indexing section to prevent relative rotationbetween said collar and said body and a second position in which saidcollar may rotate relative to said body, a ferrule for receiving an endportion of said optical fiber cable and dimensioned to extend from saidopening in said front face; and a biasing member to bias said collartowards said first position.
 10. The optical fiber connector kit ofclaim 9 wherein said terminus locking member is dimensioned to engagesaid terminus locking surface within said receptacle.
 11. The opticalfiber connector kit of claim 9 further including an arcuate recessthrough which said terminus locking member may rotate from a firstinsertion position to a second locked position to lock said terminuswithin said receptacle.
 12. The optical fiber connector kit of claim 11wherein said terminus locking member is a boss extending from saidterminus and said receptacle includes said arcuate recess therein. 13.The optical fiber connector kit of claim 12 wherein said arcuate recessincludes a step for receiving said locking tab therein when saidterminus is locked in said cavity.
 14. The optical fiber connector kitof claim 12 including a first opening in said first face and a secondopening in said second face, said ferrule extending through said firstopening, said second opening being round with a slot extendingtherefrom, and said locking tab, said arcuate recess and said slot aredimensioned to permit said tab to pass through said slot and travel tosaid arcuate recess.
 15. The optical fiber connector kit of claim 14wherein said slot extends in a direction parallel to said central axisand along an edge of said round second opening.
 16. The optical fiberconnector kit of claim 9 wherein said receptacle has a forward walladjacent said first face and wherein said elongated body has a forwardshoulder engaging said forward wall within said receptacle, said biasingmember exerting a spring force to bias said forward shoulder againstsaid forward wall.
 17. The optical fiber connector kit of claim 13wherein said receptacle has a forward wall adjacent said first face andwherein said elongated body has a forward shoulder engaging said forwardwall within said receptacle, said biasing member exerting a spring forceto bias said forward shoulder against said forward wall and bias saidlocking tab within said step in said arcuate recess.
 18. An opticalfiber connector comprising: a connector housing having at least onegenerally cylindrical receptacle for removably receiving an opticalfiber terminus therein, said receptacle having a central axis andcircular cross section; an optical fiber terminus within saidreceptacle, said terminus including an elongated body having a passagealong the central axis of said receptacle with a portion of said opticalfiber cable extending therethrough, said body further including anindexing portion, a ferrule secured to said first section of said bodyand having an end portion of said optical fiber cable therein, a collarpositioned on said elongated body and having an engagement portion forengaging the indexing portion, the collar being movable along saidcentral axis between first and second operative positions, said firstoperative position being wherein relative rotational movement betweensaid collar and said body is prevented and a second operative positionin which said collar may rotate relative to said body, and a biasingmember to bias said collar towards said first position; and wherein saidhousing includes a first engagement structure and wherein said opticalfiber terminus includes a second engagement structure, said first andsecond engagement structures interacting to retain said terminus withinthe housing.
 19. The optical fiber connector of claim 18 wherein saidfirst engagement structure is disposed within said receptacle.
 20. Theoptical fiber connector of claim 18 wherein said first engagementstructure is spaced from an opening in a rear face of the housing.
 21. Amethod of assembling an optical fiber connector, comprising the stepsof: providing an optical fiber connector having a housing with at leastone generally cylindrical receptacle for removably receiving an opticalfiber terminus therein, said receptacle having a receptacle axis;providing an optical fiber terminus, said terminus including anelongated body, a collar and a biasing member, said elongated bodyhaving an indexing section and a passage with a portion of optical fibercable extending therethrough, said collar being movably positioned onsaid elongated body and having an engagement section to engage saidindex section to prevent relative rotation between said collar and saidbody, and said biasing member biasing said collar relative to saidelongated body towards maintaining engagement of said index section andsaid engagement section; testing the terminus for insertion loss todetermine a position of optimum operational angular orientation,orienting the elongated body relative to the collar at the position ofoptimal operational angular orientation; utilizing the biasing member tosecure said elongated body relative to said collar in order to maintainsaid body relative to the collar at the position of optimal operationalangular orientation, and inserting said terminus into said receptaclealong said receptacle axis; and rotating said terminus within saidreceptacle to lock said terminus within said receptacle.